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Comment by dllu | Hacker News Reader

I once did a project to do multilateration of bats (the flying mammal) using an array of 4 microphones arranged in a big Y shape on the ground. Using the time difference of arrival at the four microphones, we could find the positions of each bat that flew over the array, as well as identify the species. It was used for an environmental study to determine the impact of installing wind turbines. Fun times.

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Reminds me of Intellectual Venture's Optical Fence developed to track and kill mosquitoes with short laser pulses.

As a side-effect of the precision needed to spatially locate the mosquitoes, they could detect different wing beat frequencies that allowed target discrimination by sex and species.

Where can I buy one?

I don't think you can. This kind of laser devices is wildly dangerous.

Correct your vision and your mosquito problem in one easy purchase.

You won't see another mosquito - guaranteed!

This laser mosquito killer is, and always has been, a PR whitewashing campaign for Intellectual Venture's reputation.

This device has never been built, never been purchasable, and it is ALWAYS brought up whenever IV wants to talk about how cool they are.

And I say this as someone who loosely knows and was friends with a few people that worked there. They brought up this same invention when they were talking about their work. They eventually soured on the company, once they saw the actual sausage being made.

IV is a patent troll, shaking down people doing the real work of developing products.

They trot out this invention, and a handful of others, to appear like they are a public benefit. Never mind that most of these inventions don't really exist, have never been manufactured.

They hide the extent of their holdings, they hide the byzantine network of shell companies they use to mask their holdings, and they spend a significant amount of their money lobbying (bribing).

Why do they need to hide all of this?

Look at their front page, prominently featuring the "Autoscope", for fighting malaria. Fighting malaria sounds great, they're the good guys, right? Now do a bit of web searching to try to find out what the Autoscope is and where it's being used. It's vaporware press release articles going back 8 years.

Look at their "spinouts" page, and try to find any real substance at all on these companies. It is all gossamer, marketing speak with nothing behind it when you actually go looking for it.

Meanwhile, they hold a portfolio of more than 40,000 patents, and they siphon off billions from the real economy. Part of their "licensing agreement" is that you can't talk badly about them after they shake you down, or else the price goes up.

They are rent-seeking parasites.

I did a similar project at 18. Needless to say I didn't have enough HW and SW skills to do much since I implemented the most naive form of the TDOA algorithms as well as the most inefficient way of estimating the time difference through cross correlation. I still learnt a lot and it led me to eventually getting a PhD in SAR systems, which are actually beamformers using the movement of the platform instead of an array

What were the results of your study? I’ve heard that bat lungs are so sensitive that when they fly across the pressure differential of large turbines their capillaries basically explode

Yes basically. Bird lungs are relatively rigid, open at both ends like a tube, and have a one-way flow of air, so they are less prone to pressure-related injuries. Bat lungs are mammalian lungs that expand and contract as they breathe just like us, so they are particularly vulnerable to barotrauma near wind turbines.

After writing a bunch of MATLAB code to find the bats, I handed it off and haven't heard back about whether they actually built the wind turbines or not.

I would love to do something like that to track the bats in my garden, how feasible would it be for an amateur to do as a personal project? Any good references on where to start.

A nice mention about this is the outstanding and quiet work of the Cosys-Lab of the University of Antwerp. They once put a microphone array below a scorpio, and showed how bats moved their ultrasonic beam to scan for a scorpio. Incredible stuff [0].

[0]: https://www.youtube.com/watch?v=57ScSPWhGqU

I had no idea they were mammals until this comment. I thought they were furry birds!

It is not unreasonable to think of bats as flying mice.

In Swedish that is almost exactly what they are called, bat translates to "fladdermus" which is "fladder" (flutter) and "mus" (mouse).

Same in German, die Fledermaus. In fact, in English, the word "flittermouse" also means bat [1], although that word is rarely used now.

[1] https://en.wiktionary.org/wiki/flittermouse

That sounds super interesting. Is there a write up somewhere of the project?

Here's the report [1], written when I was a second year undergrad in 2010.

It's very basic. The species identification is based on matching contours of the spectrogram against some template contour. The multilateration was, embarrassingly, done by brute force by generating a dense 3D grid. At the time, I didn't have any knowledge of Kalman filters or anything that could have been helpful for actually tracking the bats.

[1] https://daniel.lawrence.lu/public/bat-report.pdf

Thanks! And pretty great for 2nd year undergrad!

That sounds like a fun project. Was it part of a research grant?

> bats (the flying mammal)

As opposed to?

Baseball bats?

Here is a nice article on a study of baseball bats using microphones. https://www.acs.psu.edu/drussell/bats/papers/AcousticsToday_...

Honestly, that sounds like amazing work. I wish I could afford to get out of enterprise software engineering and just do academic software development like that.

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